In order to solve the problem of high power consumption in wide range measurement of flow velocity caused by low temperature coefficient of resistance (TCR) of commonly used metal thermistors materials such as platinum, a flexible MEMS thermal flow sensor with low power consumption and wide range based on amorphous germanium (a-Ge) film thermistors was designed. The a-Ge thermistor material has high TCR coefficient (about -0.02/K) and room temperature resistivity (5Ω·m), which makes the sensor can achieve a wide range of flow velocity measurement under low working temperature difference and power consumption. The design structure, working principle, 3D finite element modeling and thermal-flow field simulation results of the flexible MEMS flow sensor are described. It uses four a-Ge thermistors in the cavity film of flexible polyimide substrate as self-heating heat source and temperature measuring element at the same time. These four a-Ge thermistors form a Wheatstone bridge, which combines the principles of heat loss and thermal temperature difference to achieve a wide range of flow velocity measurement and direction finding. The simulation shows that the constant current power supply of Wheatstone bridge only needs 120μA, so that the temperature difference between the working temperature of a-Ge thermistors and the ambient temperature is no more than 6K, the flow velocity in the range of 0~50m/s can be measured, and the power consumption is within 1.368mW. This flexible flow sensor is easy to be fabricated in batches by using MEMS technology and can be applied to curved surfaces, which is very suitable for low-power flow sensing fields such as the Internet of Things.